[Equest-users] The question about the system type of HVAC

Bruce Easterbrook bruce5 at bellnet.ca
Sat May 17 08:10:18 PDT 2014

I assume you are talking about energy usage with the big difference.  It 
depends on how you have the defaults set up but I think you will find 
the system with the larger energy usage is reheating the air in the 
cooling season.  It is exercising humidity control by over cooling the 
air with the cooling coil to knock more moisture out of the air stream 
then heating the air up to not over cool the people in the space.
This method is frowned upon right now as it isn't very energy efficient 
if you are running your boilers in the summer time to provide the reheat 
and running a second set of pumps to move the hot water.  It actually is 
pretty much banned in some jurisdictions by energy conservation 
regulations.  It is the best way to control humidity in the air stream.  
There are some great ways to make it more energy efficient by using the 
heat off the cooling system so you don't have to use the boilers.  So 
using free heat you just have dual pumping energy as the draw back but 
considering all the other methods deployed such as DOAS and it's 
associated costs I personally don't think in the end there is much of an 
energy penalty.  It would probably be a much cheaper system to construct.
I'm a bit of a contrarian and don't like a lot of the new green rules 
that put a straight jacket on my ability to design the best system for 
the situation.
Bruce Easterbrook P.Eng.
Abode Engineering

On 17/05/2014 09:57 AM, 黄永村 wrote:
> Everyone, I am a learner ,now I have a question about the system type 
> of HVAC .When the cooling source is chilled water coils and the 
> heating source is hot water coils ,the system type of HVAC have many 
> choices, such as Standard VAV with Hot Water Reheat and Reheat Fan 
> System with Hot water Reheat. In the Air-side system type of the 
> Wizard interface, the parameter information is no differences between 
> the two system type(Standard VAV with Hot Water Reheat and Reheat Fan 
> System with Hot water Reheat),but the result  is so difference.I want 
> to know the two system where is different?
> I am sorry that my English is not better .thank you again.
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